Status of studies in the ATF Torsatron

Summary form only given. In recent experiments, beam-heated plasmas have been produced which remain quasi-stationary for times on the order of 150 ms. Global confinement times of 20 ms have been obtained with beam heating powers greater than 1 MW (up to 27 kJ at 1.9 T). The highest <β> of 0.84% was obtained with pellets at 0.95 T. In ion cyclotron resonance heating (ICRH) experiments with up to 180 kW launched into plasmas with D⁺ majority and H⁺ minority (with minority fractions less than 10%), minority tails out to 40 keV were obtained, and no significant influx of impurities was observed. In electron cyclotron heating (ECH)-only plasmas, the small toroidal current has been identified as bootstrap current. Its behavior and magnitude with configuration changes created by systematic scans of the quadrupole and dipole components of the vertical fields are consistent with neoclassical theory. A comparison of edge fluctuation phenomena found in the current-free ATF and in the TEXT tokamak has shown some similarities. The magnitude of the fluctuation-induced particle flux is consistent with global particle confinement in ATF